Recently, a variety of variable geometry turbochargers (VGTs), that aim to address boost issues, have become available. VGTs, such as, but not limited to, the GARRETT® VNT™ and AVNT™ turbochargers (Garrett Corporation, California), use adjustable vanes, nozzles or the like, to control exhaust flow across a turbine. For example, GARRETT® VNT™ turbochargers adjust the exhaust flow at the inlet of a turbine in order to optimize turbine power with the required load or other conditions. Movement of vanes towards a closed position typically directs exhaust flow more tangentially to the turbine, which, in turn, imparts more energy to the turbine and, consequently, increases compressor boost. Conversely, movement of vanes towards an open position typically directs exhaust flow more radially to the turbine, which, in turn, reduces energy to the turbine and, consequently, decreases compressor boost. Thus, at low engine speed and small exhaust gas flow, a VGT turbocharger may increase turbine power and boost pressure; whereas, at full engine speed/load and high gas flow, a VGT turbocharger may help avoid turbocharger overspeed and help maintain a suitable or a required boost pressure.
A variety of control schemes exist for controlling geometry in variable geometry turbines. However, such schemes often exhibit time lags, hysteresis, and other characteristics that can compromise or limit geometry control. Thus, a need exists for new control schemes that can overcome such limitations. Methods, devices, systems, etc., for sensing and/or controlling geometry in variable geometry turbines are described below.